Reinforcement fibre for reinforcing concrete

Abstract: Reinforcement fibre (1) made of metal for the reinforcement of concrete, consisting of a wire piece, which is deformed near both ends over a certain distance. The wire piece is undeformed between the ends and the deformed part. The two extremities of the reinforcement fibre are not deformed over a distance of 1 to 5 mm. The reinforcement fibre is provided with a profiling consisting of a large number of small notches or grooves (5). The grooves are provided at an angle to the longitudinal axis of the reinforcement fibre. The length of the reinforcement fibre lies between 10 and 70 mm, and the fibres have a length-thickness ratio of between 40 and 70. The ends of the reinforcement fibre are bevelled (10) at an angle of approximately 45 degrees and are slightly flattened. The transition from the deformed part to the undeformed part is provided with a slight bulge (9).

Description: The invention relates to a reinforcement fibre made of metal, preferably of steel, for the reinforcement of concrete, which reinforcement fibre consists of a straight wire piece, which is deformed near both ends over a certain distance. Such wire pieces or reinforcement fibres are commonly used for adding as a reinforcement to mortar or concrete, in order to increase the strength of the concrete. The tensile strength of the set concrete is then increased in all directions. Such a fibre is known from the American patent US-A 4,233,364. This known fibre consists of a metal wire piece with deformed, flattened parts near the end. These flattened end parts cause two shape transitions. However, the anchoring effect of these transitions is limited and is improved by means of additional projections at the ends. Such a fibre is however expensive to produce. Since the additional projections can hook into each other, such fibres are difficult to mix homogeneously with concrete. The object of the invention is a straight reinforcement fibre which shows an improved anchoring effect and which can be produced in an efficient and inexpensive way. This object of the invention is achieved by a reinforcement fibre according to the invention through the fact that the distance over which the wire piece is deformed, is smaller than ten times the thickness of the wire piece and greater than three times the thickness, in such a way that the thickness of the deformed part lies between 0.2 and 0.6 and the width lies between 1.5 and 3 times the thickness of the wire piece and in that the deformed part of the wire piece begins at a distance from both ends, which distance lies between zero and five times the thickness, while the wire piece is undeformed between the ends and the deformed part. It appears that by designing the fibre according to the invention the force required to pull the fibre out of the concrete has become much greater than was the case until now with comparable fibres known hitherto. When the deformed part begins at distance from both ends, the straight fibre according to the invention shows four shape transitions as a result of only two deformed parts. By deforming parts at a distance from the ends in stead of at the ends, four shape transitions are obtained in stead of two. Due to these four shape transitions, the resistance has become very great if a force is exerted in the lengthwise direction of the fibre. Another advantage of these straight reinforcement fibres is that balling or caking together will not occur, in contrast to, for example, fibres which are provided with bent ends or with hooks. The reinforcement fibre is preferably designed in such a way that the ends of the reinforcement fibre are bevelled at an angle of approximately 45 degrees and slightly flattened. This has the advantage that the reinforcement fibre is less exposed to bending or crushing stress when the enclosing concrete is put under pressure. The reinforcement fibre can also be produced in such a way that the transition from the deformed part to the undeformed part is provided with a slight bulge. This means that tension concentrations are avoided and the reinforcement fibre is strengthened. The external surface of the fibre is preferably roughened, for example through notches at right angles to the longitudinal axis of the fibre or slanting at an angle to the longitudinal axis. Another possibility is to make a helical or corkscrew-type groove on the external surface of the fibre. The invention will be explained in greater detail with reference to the drawing. In the drawing: Fig. 1 shows a top view of the fibre according to the invention; Fig. 2 shows a side view of the fibre according to the invention from Figure 1; Fig. 3 shows greatly enlarged the flattened end part of the fibre according to the invention; Fig. 4 shows diagrammatically the type of deformation occurring at the transition from the flattened part to the round shape of the fibre; Fig. 5 shows a detail of the fibre with notches; Fig. 6 shows a side view of an alternative embodiment according to the invention; Fig. 7 shows a top view of the embodiment according to Figure 6. Figures 1 and 2 show two views of the reinforcement fibre 1 according to the invention. The reinforcement fibre 1 consists of a piece of steel wire 2 with a circular cross-section. Near the two ends 3 of the fibre 1 a part 4 is deformed. Through the flattening, for example with a roller, a part of the wire has become broader in one direction and thinner in the other direction. In this embodiment of the reinforcement fibre according to the invention, the surface of the fibre facing upwards and downwards is provided with a number of notches 5. Figure 3 shows in greater detail a greatly enlarged flattened part 4, while Figure 4 shows a number of successive cross-sections of the fibre 1 at the point where the wire is deformed. This deformation occurs both at the one side 6 of the flattened part 4 and at the other side 6 of the flattened part 4, at the point where the flattened part 4 again passes into a small part 7 of steel wire or reinforcement fibre, and goes up to the end of the reinforcement fibre 1. Figure 4 shows in the same figure a number of successive cross-sections through the transitions 8 and 9 of the flattened part 4 to the round part of the fibre 1. Figure 5 shows in longitudinal section a part of the fibre at the point where it is provided with notches 5, which are provided in principle on two surfaces lying opposite each other, in such a way that all notches on the top side are staggered alternately in relation to the notches on the bottom side. The embodiment in which the notches are provided at an angle to the longitudinal axis of the fibre is not shown. Figure 6 shows another embodiment according to the invention. The reinforcement fibre 1 is flattened near the ends 3 over a part 4. The bottom side 8 in this case has remained flat. The transition between the flattened parts 4 and the undeformed parts of the reinforcement fibre 1 is provided with a bulge or rib 9. The shape transition is consequently less sharp at that point. This means that tension concentrations are avoided and the reinforcement fibre 1 is strengthened. The reinforcement fibre 1 is also provided with slightly widened and bevelled ends 10. This produces new shape transitions at those points, which make the reinforcement fibre 1 anchor even better in the concrete. The bevelled ends 10 prevent the reinforcement fibre 1 from being subjected to bending or crushing stress when the surrounding concrete is subjected to pressure. Figure 7 shows the same reinforcement fibre as that of Figure 6, but in top view. It appears that this method of anchoring the reinforcement fibres in concrete ensures that they remain very well anchored, and the full fibre length can be used to absorb forces. Moreover, these fibres are straight and therefore very easily mixed through the mortar, and it has been found that no balling of the fibres occurs. Of course, the invention is not limited to the embodiments discussed here, the extend of the protection being determined by the terms of the claims. It is also possible to deform several parts of the fibre so that the fibre is alternately round and flattened, for example, over distances varying from 0.5 to 5 mm, and the flattened parts are also sometimes alternately rotated a quarter turn relative to each other. Such straight fibres with alternately flat and round parts of, for example, 3 mm are, of course, even more resistant to pulling out in the lengthwise direction, but more working operations have to be performed in order to produce such fibres.

Claims: Reinforcement fibre made of metal, preferably of steel, for the reinforcement of concrete, which reinforcement fibre consists of a straight wire piece, which is deformed near both ends over a certain distance, characterized in that said distance is smaller than ten times the thickness of the wire piece and greater than three times the thickness, in such a way that the thickness of the deformed part lies between 0.2 and 0.6 and the width lies between 1.5 and 3 times the thickness of the wire piece and in that the deformed part of the wire piece begins at a distance from both ends, which distance lies between zero and five times the thickness, while the wire piece is undeformed between the ends and the deformed part. Reinforcement fibre according to claim 1 characterized in that the ends of the reinforcement fibre are bevelled at an angle of approximately 45 degrees. Reinforcement fibre according to one of the preceding claims, characterized in that the transition from the deformed part to the undeformed part is provided with a slight bulge. Reinforcement fibre according to one of the preceding claims characterized in that the reinforcement fibre is provided with a profiling consisting of a large number of small notches or grooves. Reinforcement fibre according to claim 4, characterized in that the grooves are provided at an angle to the longitudinal axis of the reinforcement fibre. Reinforcement fibre according to claim 4, characterized in that the profiling consists of a corkscrew-type groove around the external surface of the reinforcement fibre.

Inventors: OVER ALFRED WILHELM, OVER ROBERT HUGO JACOB, OVER, ALFRED WILHELM, OVER, ROBERT HUGO JACOB
Applicants: METALMIX B V, OVER ROBERT HUGO JACOB, METALMIX B.V., OVER, ROBERT HUGO JACOB
Application year: 1994
Main classification: E04C5
IPC codes: E04C5